Process of rolling sheets



Oct. 12 1926. 1,602,468

J. B. TYTUS PROCESS OF ROLLING SHEETS Filed March 12. 1923 By W ATTOR/Vf/S.

Patented Oct. 12, 1926.

; UNITED STATES PATENT OFFICE...

JOHN B, TYTUS, OF MIDDLETOW N, OHIO, ASSIGNOR TO THE AMERICAN ROLLING MILL COMPANY, OF MIDDLETOWN, OHIO, A CORPORATION OF OHIO.

rnocnss or I nornnte snnn'rs.

. Application filed narch112..ia2a.',sm1 No. 624,632;

My invention relates to the continuous Two or more stands will satisfy this defini-. lotion 7 There have been in the past a. large numher of theoretical suggestions forthe rolling of sheet metal to finished gauge bya continuous process. In a'few instances con' tinuous mills, socalled,.althouglr'somewould have been better classed as tandem mills, f have-been built and need in sheet rolling.-

So tar as I am advised with the:e mills, it

was always thepractice to finish the packs.

or-doubles, from the "continuous process, in

a'single stand of finishingrolls, accordingto the Wel's'h system of rolling. This was true, for example, of'the well known Bray mills widely referred to in all modern discusrions of thesubject of rolling sheets.

Thus my inventiomwhichhas the avowed object of finishing sheets to ultimate gauge in a continuous process, has a basis which is distinct from any practical or even theoretical structure of the past,

ing will not require re-statement in this specification, as it is known at the present time, wherever steel sheets are rolled down from sheet bars. The significant reason to which has been ascribed the necessity of finishing sheets to final gauge on a single stand or rolls, is that the roller can watch ,the piece as it is being worked upon, and control his'roll draft accordingly to suit each particular piece and that the piece having been given preliminary reduction on a single stand of rolls thus acquires a fit to such peculiar variations in contour as the said stand of rolls possesses.

While the above reasons mayor may not be entirely correct, it isquite significant of the many costly experiments of the past,-

followin The discussion of the Welsh system of roll- I -my process is a pack.

v necessarilyfrom a continuous process, has rolling of metal, more part1cu1'arly packs of metal sheets or doubled sheets, to. finished always been more than overcome by the increase 111 wasters or ruined pieces, and in roll breakage, and shut downs.

Itis the specific object of my invention t0 so-design and control a rolling process, as

to accomplishjn a mechanical manner the work -which. a. skilled roller would do in finishing aspack on a" single stand of two hlgh rolls. c

. Tovthis'end I take into consideration the features which enter into any sheet rol ing method The prepared contour of the-rolls; 2) The temperature of the rolls. v

3) The composition "and springiness of therolls. I (4; The spacing of-"the rolls, or ,screw. (5 The shape, composition and temperature of the piece; I

.My ultimate aim is to so control these five factors, that a piece of a predetermined contour and predetermined temperature will be engaged in each stand-of a series of pairs ofrolls, arranged to successively engage the piece, wherein the rolls have apredetermined contour to it the piece, said roll 1 contour being the resultant of the five points above mentioned.

The rolls need not necessarily be arranged so in successive two high stands, as three or four high stands might also be used."

By piece, I refer to whatever metal is being worked on. In particular the piece in To state the matter in another way, if a piece of material of given thickness is caused to pass througha pair of rolls, which are driven so as to. pull the piece along and attenuate or reduce it, the resultant shape of the roll engagement will depend in part upon the prepared 'shape of the rolls, and the temperature thereof, which has caused such expansion as to change .this prepared contour. It will depend upon how far the journals of the rolls are permitted to space away -from each other, due to the position of the screw which forms a stop for at least one'of the rolls. It will depend upon the shape and condition of the piece and how 1 ill ' The heat to the rolls as applied by the piece.

till

' resilient the rolls are when at the temperature and under the resultant pressures in question.

When a piece isen gg by the m the.

ly on a slight concavity, this concavity is usually taken up by the heating of the roll;

itself, which is often red hot, is more quickly dissipated at the ends of the roll, with the result of a pufing out of the center thereof.-

The composition and condition of the rolls? affect the pufing tendency, and external treatment of the rolls and journalsare usual ly employed as controlling means in the temperature, shape factor thereof.

The shape of the piece to start with, has

also a deciding eflect upon the contour of the active pass, or space between the rolls, whilethe piece is between them, particularly when the piece is thin, as a convex piece will naturally tend to afiect thespring of the rolls in a difierentway from a truly rec tangula'r piece. r

it should be noted that in speaking of contour of a pack of sheets, a sheetbar, or the like, 1 am not referring to any shape which would be apparent to the eye, as the variations over a true straight line to the active pass or space between the rolls-while a piece is between them, is not apparent to the eye. The contour or active pass is quite apparent, however, by the examination of the piece,

for at the point where the space between the rolls is less than at another, there will be a greater extension of the piece.

My method of successive or continuous rolling operates best in a set of rolls so arranged that the piece is in only one stand at a time, and, while l have no knowledge which will necessaril eliminate the use of the continuousmill, i prefer to use a tandem or other arrangement. The distinction between a continuous mill and a tandem mill is that while each has a succession of rolls, that in the tandem mill the piece emerges from one set of rolls before it is engaged by another, and in the continuous mill the piece is engaged by at least two of the stands at one time. Other arrangements of stands of rolls would be to stagger them or arrange fine myself to any type of mill but refer to the progression of. the piece through a series of stands of rolls, in any arrangement.

in the continuous mill the error which may enter into the rolling in one stand, may 210- cumulate or increase, in the second stand incense without a chance of correcting it, and particularly the continuous mill re u1res a delicacy of adyustment of roll spec s which is aproblem that adds great additional difficulty to the design of the mill. This last I is because the piece being longer as it emerges from the first mill will demand a greaterspeed in the second mill to move the piece along without an accumulation between the two stands.

By referring to sheets, ll do not desire to be construed as relying upon-any one of the current technical definitions between sheets and plates, and between sheets and strips, as the demarcation which I desire to make, is

essentially ll produce a thin metal piece which is considerably wider than it is thick.

Technically the trade in speaking of sheets refers to thin flat pieces of which the separate pieces making it up (as in a pack) have eighteen gauge (U. S. Standard) or higher and the width of an 18 gauge sheet will ordinarily be more than 400 times greater than its thickness.

' A better way of defining the'kind of material with which l deal, is by comparison thereof with. hot rolled strips. Thus a hot rolled sheet or thin plate in the terminology of the art refers to a piece which be cause of exigencies of process can not be made in a long continuous body, mainly because of the relative width to thickness thereof, whereas a hot rolled strip is a piece which from exigencies of process has distinct limitations in width and thickness, but no limitations as to length. The products which ll make and to which I refer fall into the first of these classes.

vide by -the regulation of the elements above discussed for the production of a piece in It is the-essence of my process, that l proeach stand of rolls which has a convex'cone tour which is slightly more convex than the resultant active pass of the next stand of rolls, considering each active pass in the series as a resultant of the factors outlined.

Thus the preferred manner in which l provide a mechanism for my process consists in first determining the diameter of the rolls and their physical structure, and cutting their surfaces with a concavity, iii on or both rolls of each pair, which at a given screw and temperature, thickness and contour of piece will give a resultant convexity of active pass when the piece is between them. 1 control the temperature of the rolls by external means, and control the temperatureof the piece, preferably, by furnaces orheaters between the stands of rolls.

in carrying out my process, the roller must lreep in mind the five factors recited, and use them, in the manner with which he will be familiar, in conjunction with each 'the rolls are not springy enough 'in their composition, it may be that his piece istoo hot, or improper screw with relation to heat of the the di culty may be t at the piece is too convex in cross section, or not convex enough, the latter being the most probable.

The skilled roller knows how to control these factors recited, if he knows the effect to be gained, although ofcourse', the usual skilled roller would not be familiar with the bearing of the several factors on each other, along the theoretical lines set forth in this specification.

Atypical instance in the rolling mill as operated by me will be as follows :-'A roller is given a test piece which he knows will. have a convexity alike to the pieces he is to handle on a given run. He will pass this piece through stand after stand of the rolls, and place a gauge upon its edges and middle. If the passes are very bad, of course, the gauge need not be used, as he will know ther is something wrong and can see with the eyethat he is drawing the edges or middle out too long thereby curling up or buck-.

ling the piece.

Having run the test piece or several test pieces, he will by his gauge, or by his eye when h grows skilled in the new practice outlined by me, gain a setting of his rolls which provides an active pass in each stand which is less convex than the piece delivered to it from the preceding stands. Having set his rolls, he will start the packs through the stand without changing them further except in case of trouble when he will again check up by gauge or by eye for progressively less convexity of active pass.

He will naturally be provided with the usual expedients for control of heat on the piece and rolls, control of screw and with knowledge of the starting contour of the pieces he is going to roll.

As a typical analysis of a single instance of proper mod of reduction I give a'table' of dimensions in cross section of a typical pack in three stages of successive reduction in consecutive passes through three stands of rolls, the numerals being in inches of thickness, the pack being 30 inches wide.

I Starting. After first pass. j Edge .1875 Edge .1423. Middle .1965 Middle .1491

After second pass. 7 After third pass. Edge .1146 Edge .096- Middle v.1201 Middle.. .1005

iece has been applied. Then again- The active passes are all convex, although the last one shows very litttle difference between edges and middle. Also it would be possible and practical to vary from the exact figures given above in treatment of the given piece to gain the given final gauge.

In practice the final gauge is a fixed requirement on any one order, as is the arrangement of the active pass in each stand to reduce the middle more than the edges and still preserve some convexity' Also, of

course, the maximum number of passes 1s a fixed quantity. 1

Given the starting convexity of the pack,

the number of active passes, and the final gauge to be rolled, the operators can readily calculate a similar table to the above, although as I have stated an absolute and mathematically exact. correspondence to the example given, in the several active passes,

is by no means required.

I should-also observe, that due to the fact that when the convexities have been provided for properly, which the skilled roller can do readily if he regards the five factors which I have given above, and will further speak of, it will be found that the pack as it enters and passes each stand will lie smooth and feed accurately through the center of the roll stands. Thus it might readily be possible that the skilled roller could in a given instance working merely to the end of getting a smoothpass, hit upon a proper control of his roll bite in individual stands, but it would be next to impossible for him, without knowledge of the necessity-of control of the five factors I have given, and the rule of convexity reduction, (i. e. greater reduction of thicker than thinner parts of the piece) for himto handle all of the stands by rule of thumb, or to adjust the stands for diflermore readily will it take the contour which is desired without bad results,and if for example I' provide a pack or doubled-up body of thin plates, according tothe Welsh system, this pack will naturally have a dethe spring in the rolls which formed the individu'al plates 1 from which the packis I made. It is preferable towatch closely-the formation of the plates from which the packs are formed, so that the starting contour is exactly right, although as stated, the thickness of the piece makes errors'one way or the other ofnot ,so' uch importance at the start 'cided convexity of contour, resulting from In the drawings Figure 'l. is a side 'eietion. of three tandem rolls in with an exaggerated illustration oij'three pieces passing between the rolls. I Figure 2 is a section diagram, exaggerated to-illustrate the pass through thehrst stand. Figure IS a like view lor the second stand and Figure l 4: for the third stand,

l: have illustrated in diagram three sets or? rolls (two high),- at l, 2 and hialthough it will he understood that more stands-could he added, The piece is illustrated at 1, 2

and 3 lin section in Figure 2 is shown the progresslve convexity oi'the piece, during itsreduction. The convexity is, as has been said, not apparent to the eye and has heen exaggerated. The piece may he a pack of sheets, or a single plate to begin with.

The space between the rolls is defined lay the lines It, 2 and 8", these lines illustrating, by the space between them, the active pass of the rolls. v

it will preferably start with a piece itormed of plates of the type known as lire bed plate. These plates may he formed in a tandem mill, and'when trimmed and piled .or "doubled should be arranged so that the lengthwise components of the plates in a pack are in line with each other,v Thus any crest or convexity on the. plates will be added together to produce a pack of a curve of convexity having ashorter diameter than that of any individual plates making it up.

The reasons for maintaining the contour as l have stated are many, but. it will sufiice to point out, that with a convexity slightly less than the convexity of the pre- I ceding pass, there will be a tendency of the rolls in a pass in question to line up the piece With the crest of convexity running through the crest of the convex active pass between the rolls.

Also, as the thickness of the piece becomes reduced, and the amount of screw on the rolls, and hence pressure exerted in attenuating the piece, must be varied to efiect the desirable reduction l have found that if the various elements going into the result of a sheet rolling action are controlled so -true function of the special design of rolls,

heating devices, and the like will operate to the end above outlined. The saving in the-services oi assistants is very Loss while they are in engagement with the piece being rolled therebetween;

I do not desire my specification above to he construed as limitation to the claims "J follow, wherein it is my desire the iiull application of the doctrine of equivalents he followed in their construction. 4

.Having thus described my invention, what I claim as new and desire-to secure by Letters Patent, iszlad continuous process for reducing hot metal to sheet form in successive stands of rolls, which consists in passing a piece of metal from one stand to another successively and controlling the active pass oi the rolls in each stand so as to form for the next stand a piece of slightly greater convexity than the active pass or" said next stand.

2. A continuous process for reducing hot metal to thin Wide form in successive stands of rolls which consists in passing a piece oi metal through one stand of rolls after an other successively and impressing upon the piece by the active pass of the first and each succee'dingstand of rolls, a cross sectional shape of other than parallel surfaces, which will be made more ncarlyparallelsurfaces in each active pass.

3. A continuous process for reducing hot metal to sheet-like form which consists in passing a piece or metal through one stand of rolls after another successively, and pro 'viding an active pass in each stand of rolls, of different predetermined. non-parallel sided contour.

Q. A continuous process for reducing a pack or doubled mass of plate metal to sheet form, insuccessive stands of rolls, which consists in passing a piece of metal from one stand to. another successively and controlling the active pass of the rolls in each stand on said pack 50 as to deliver to the next stand a piece which has a slightly greater convexity than the active pass or said next stand. 1

.5. That process of reduction of metal to sheet form, which consists in forming a pack or doubled mass of plate metal, in which the arrangement is such that the line of feed of the pack will be a continuation of the line of teed in forming each plate thereof, and at suitable temperature. passing said pack through successive stands of finishing rolls, and in each stand controlling the active pass of the rolls so as to produce a piece having-a slightly less convex form than was the form of the piece when delivered to it.

6. A continuous process for reducing hot metal to sheet-like form which consists in 5 passing a piece of metal through one stand of rolls after another successively, and providing an active pass in each stand of rolls,

of predetermined contour, said contour being one which will cause the piece to pass through the middle of each succeeding active pass, but the final contour being Within the tolerances of accepted commercial variation as to uniformity of gauge and flatness.

JOHN B. TYTUS. 

